I own a commercial laundry and I'm somewhat mechanically inclined but not an engineer We recently tried some new equipment from Germany sold by MerusUSA which is supposed to be installed on the inlet side (either the tube side or shell side). Our heat exchanger is very old and since it has never been opened, it probably does have rust, scale build up in it. Lesser the scale, better the efficiency. It was placed on the shell side on Aug 6th 2007(Summer). At the time of installation the difference between the in and out was from 89 deg to 92 deg. that is the difference of 3 deg F. I was told by the local rep that the cleaning of heat exchanger will take approx 4-6 months. We inspected the difference today and it was from 52 deg(inlet) to 59 deg F. (outlet) The difference of 7 deg F. It's in at 52F because it's raw water and it's winter offcourse. The engineer in charge thought the difference was due to the cold weather and she wishes to continue data collection thru the coming summer. ( as the ring was installed in summer) My questions are: Since the summer the temperature difference was 92 minus 89 = 3 Degrees. Now the difference is 59 minus 52 degrees = 7. 1) What does this mean in efficiency in temperature difference mean? I can presume that the scale removed in the shell caused a difference of 4 more degrees? Is there some data available on what this means for me? 2) Should these temperature difference readings be taken in summer instead of now? Or it doesn't matter? I'm thinking of buying this equipment and that is reason I wanted to be sure. Any help would be great.